Polycarbonate and optical material

ABSTRACT

Disclosed are polycarbonates which are obtained by preparing a polycarbonate prepolymer through prepolymerization followed by polymerizing it through solid-phase, swollen solid-phase or thin film melt-phase transesterification, and have a remaining monomer content of smaller than 100 ppm, especially a dihydroxy compound content of smaller than 100 ppm, or have an acetone soluble content of at most 3.5 or at most 3.0% by weight, or have a terminal hydroxyl fraction of smaller than 2 or smaller than 15 mol %; and optical materials and blow molding materials comprising the polycarbonate. The polycarbonates contain a reduced amount of impurities such as remaining monomers, oligomers and others and have improved physical properties including impact strength, and these are useful as optical materials and blow molding materials.

FIELD OF THE INVENTION

The present invention relates to polycarbonates, more precisely to thosehaving a reduced content of impurities such as remaining monomers andoligomers and having excellent physical properties such as impactstrength, and also to optical materials and blow molding materials.

DESCRIPTION OF THE BACKGROUND

Polycarbonates are excellent engineering plastics and are widely used invarious fields. For producing them, known are a method of directlyreacting an aromatic dihydroxy compound such as bisphenol A or the likewith phosgene (interfacial process), and a method of transesterifying adicarbonate such as diphenyl carbonate or the like with an aromaticdihydroxy compound such as bisphenol A or the like in a melt:or solidphase (melt-phase process, solid-phase process).

However, the interfacial process is problematic in that it requirestoxic phosgene, the chlorine-containing side products such as hydrogenchloride, sodium chloride and the like formed corrode the apparatusused, and methylene chloride that may be in the resins formed isextremely difficult to remove and therefore the polycarbonates formedoften contain chlorine.

On the other hand, the melt-phase process is free from the problems withthe interfacial process, but is confronted with another problem in thatthe amount of monomers and other low-molecular-weight substancesremaining in the polymers produced is large. As a result, the impactresistance of the polymers is low, and the polymers often adhere tomolds.

To solve the problems, a method of adding a low-boiling-point compoundto extruders in the melt-phase process has been proposed (JapanesePatent Laid-Open No. 5936/1997), but it is not still satisfactory.Neither proposal nor report is known, relating to the improvement in thesolid-phase process.

The present invention is to solve the problems with polycarbonatesproduced through conventional transesterification, and to providehigh-quality polycarbonates having good impact resistance and alsooptical materials and blow molding materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

We, the present inventors have assiduously studied to attain the objectas above, and, as a result, have found that high-quality polycarbonatescontaining an extremely reduced amount of monomers andlow-molecular-weight substances remaining therein can be obtainedthrough transesterification by properly selecting the reaction methodand the reaction condition to be employed. On the basis of this finding,we have completed the present invention.

Specifically, the invention provides polycarbonates described below.

[1] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough solid-phase, swollen solid-phase or thin film melt-phasetransesterification, of which the total of the dihydroxy compoundcontent, the dicarbonate content and the monohydroxy compound content issmaller than 100 ppm.

[2] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough solid-phase, swollen solid-phase or thin film melt-phasetransesterification, of which the dihydroxy compound content is smallerthan 100 ppm.

[3] A polycarbonate obtained through transesterification of a dihydroxycompound and a dicarbonate, of which the acetone soluble content is atmost 2.0% by weight.

[4] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough thin film melt-phase transesterification, of which the acetonesoluble content is at most 3.0% by weight.

[5] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough solid-phase or swollen solid-phase transesterification, of whichthe acetone soluble content is at most 3.5% by weight.

[6] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough solid-phase or swollen solid-phase transesterification, of whichthe terminal hydroxyl fraction is smaller than 2 mol %.

[7] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough thin film melt-phase transesterification, of which the terminalhydroxyl fraction is smaller than 15 mol %.

[8] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough prepolymerization followed by polymerizing the prepolymerthrough solid-phase, swollen solid-phase or thin film melt-phasetransesterification, of which the cyclic oligomer content is at most0.45% by weight.

[9] The polycarbonate of above [1], [2], [5] or [8], for which thepolycarbonate prepolymer is prepared through thermal prepolymerizationof (A) an aromatic dihydroxy compound, (B) a dicarbonate and (C) amonohydroxy compound.

[10] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough thermal prepolymerization of (A) an aromatic dihydroxy compound,(B) a dicarbonate and (C) a monohydroxy compound followed bypolymerizing the prepolymer through solid-phase or swollen solid-phasetransesterification, of which the monohydroxy compound-derived terminalfraction is at least 50 mol %.

[11] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough thermal prepolymerization of (A) an aromatic dihydroxy compound,(B) a dicarbonate and (C) a monohydroxy compound followed bypolymerizing the prepolymer through solid-phase or swollen solid-phasetransesterification, of which the terminal hydroxyl fraction is smallerthan 15 mol %.

[12] An optical material comprising the polycarbonate of any of above[1] to [11].

[13] The polycarbonate of any of above [1], [2], [5] or [8], for whichthe polycarbonate prepolymer is prepared through thermalprepolymerization of (A) an aromatic dihydroxy compound, (B) adicarbonate and (C) a poly-functional organic compound having at leastthree functional groups.

[14] A polycarbonate obtained by preparing a polycarbonate prepolymerthrough thermal prepolymerization of (A) an aromatic dihydroxy compound,(B) a dicarbonate and (C) a poly-functional organic compound having atleast three functional groups, followed by polymerizing the prepolymerthrough solid-phase or swollen solid-phase transesterification, of whichthe terminal hydroxyl fraction is smaller than 15 mol %.

[15] A blow molding material comprising the polycarbonate of above [13]or [14].

BEST MODES OF CARRYING OUT THE INVENTION

The polycarbonate of the invention includes those obtained throughmelt-phase or solid-phase transesterification of starting materials, (A)a dihydroxy compound and (B) a dicarbonate, and optionally (C) aterminating agent or a branching agent, especially those obtained bypreparing a polycarbonate prepolymer through prepolymerization of (A) adihydroxy compound and (B) a dicarbonateorphosgene, andoptionally (C) aterminating agent or a branching agent, followed by polymerizing theprepolymer through solid-phase, swollen solid-phase or thin filmmelt-phase transesterification. In preparing the polycarbonateprepolymer and polymerizing it, catalysts are used.

1. Characteristics of Polycarbonates of the Invention:

(1) In one aspect, the polycarbonate of the invention is obtained bypreparing a polycarbonate prepolymer through prepolymerization followedby polymerizing the prepolymer through solid-phase, swollen solid-phaseor thin film melt-phase transesterification, and the total of thedihydroxy compound content, the dicarbonate content and the monohydroxycompound content of the polycarbonate is smaller than 100 ppm. Thedihydroxy compound content, the dicarbonate content and the monohydroxycompound content of the polycarbonate are measured throughhigh-performance liquid chromatography in the following manner: 2 g of apolycarbonate sample is dissolved in 50 ml of dichloromethane, and 250ml of acetone is added thereto little by little so as to deposit thepolymer in the solution. This is filtered under suction, and 50 ml ofacetonitrile is added to the filtrate. This is concentrated to about 10ml. The resulting concentrate is put into a 50-ml messflask, and wateris added thereto so as to have a ratio, acetonitrile/water=1/1 (byvolume). This is filtered through a chromatography disc, 13P, andsubjected to high-performance liquid chromatography. The condition forHPLC is as follows: The column is Toso's TSKgel ODS-80Ts. The mobilephase is comprised of an aqueous acetonitrile solution (liquid A)(acetonitrile/water=3/7, by volume) and an aqueous acetonitrile solution(liquid B), in which the ratio of liquid A/liquid B is varied from 100/0(by volume) to 0/100 (by volume). With so varying the ratio of the two,20 μl of the mixture for the mobile phase is introduced into the columnover a period of 35 minutes, at a flow rate of 1.0 ml/min. For recordingthe data, a detector (wavelength: 217 nm) is used.

(2) Of polycarbonates obtained through transesterification of adihydroxy compound and a dicarbonate, especially those obtained bypreparing a polycarbonate prepolymer through prepolymerization followedby polymerizing the prepolymer through solid-phase, swollen solid-phaseor thin film melt-phase transesterification, the acetone soluble contentof the polycarbonate, for which the prepolymer is polymerized in any ofthe former two solid-phase reaction modes, is at most 3.5% by weight,while that of the polycarbonate, for which the prepolymer is polymerizedin the latter liquid-phase reaction mode, is at most 3.0% by weight,preferably at most 2.0% by weight. The acetone soluble content of thepolycarbonate is measured according to the following method: 3 g of asample of polycarbonate flakes having passed through a 100-mesh wiregauze is put into a cylindrical paper filter No. 84 (28 mm×100 mm), andextracted with 100 ml of acetone for 8 hours while being refluxed atintervals of once for 3 to 4 minutes (20 ml/once). Next, 100 ml ofacetone is evaporated away, and the residue is dried overnight in vacuumat 110° C., and its weight is measured. This indicates the acetonesoluble content of the polycarbonate sample tested.

(3) In another aspect, the polycarbonate of the invention is obtained bypreparing a polycarbonate prepolymer through prepolymerization followedby polymerizing the prepolymer through solid-phase, swollen solid-phaseor thin film melt-phase transesterification, and the cyclic oligomercontent of the polycarbonate is at most 0.45% by weight.

The cyclic oligomer content of the polycarbonate is measured accordingto the following method: 2 g of a polycarbonate sample is dissolved in50 ml of dichloromethane, and 250 ml of acetone is added thereto littleby little so as to deposit the polymer in the solution. This is filteredunder suction, and the filtrate is dried. This is dissolved in 50 ml ofdiethyl ether, then filtered under normal pressure, and dried.Chloroform is added thereto to make it have a constant volume of 20 ml.This is filtered through a chromatography disc, 13P, and subjected tohigh-performance liquid chromatography to determine the cyclic oligomercontent of the sample.

(4) In still another aspect, the polycarbonate of the invention isobtained by preparing a polycarbonate prepolymer throughprepolymerization followed by polymerizing the prepolymer throughsolid-phase, swollen solid-phase or thin film melt-phasetransesterification, and the terminal hydroxyl fraction of thepolycarbonate, for which the prepolymer is polymerized in any of theformer two solid-phase reaction modes, is smaller than 2 mol %, whilethat of the polycarbonate, for which the prepolymer is polymerized inthe latter liquid-phase reaction mode, is smaller than 15 mol %.

The terminal hydroxyl fraction of the polycarbonate is measuredaccording to the following method: A polycarbonate sample is subjectedto ¹H-NMR (400 MHz, 128 integration cycles), for which is used CD₂Cl₂ asthe solvent. On the ¹H-NMR chart, Ha and He are read, from which theterminal hydroxyl fraction of the sample is obtained according to thefollowing equation:

Terminal hydroxyl fraction=(Ha/2)/(Ha/2+He/2) wherein Ha indicates theintegrated ratio of the peaks derived from two hydrogens that areortho-positioned in the benzene ring of the terminal phenyl grouprelative to the OH group bonding to the group; He indicates theintegrated ratio of the peaks derived from two hydrogens that aremeta-positioned in the benzene ring of the terminal phenylcarbonategroup relative to COO bonding to the group.

(5) In still another aspect, the polycarbonate of the invention isobtained by preparing a polycarbonate prepolymer through thermalprepolymerization of (A) an aromatic dihydroxy compound, (B) adicarbonate and (C) a monohydroxy compound, followed by polymerizing theprepolymer through solid-phase or swollen solid-phasetransesterification, and the monohydroxy compound-derived terminalfraction of the polycarbonate is at least 50 mol %.

To analyze its terminal structure, the polycarbonate is subjected to¹³C-NMR (125.65 MHz, 24 integration cycles), for which is used CD₂Cl₂ asthe solvent. From the ¹³C-NMR data, obtained is the monohydroxycompound-derived terminal fraction of the polycarbonate.

(6) In still another aspect, the polycarbonate of the invention isobtained by preparing a polycarbonate prepolymer through thermalprepolymerization of (A) an aromatic dihydroxy compound, (B) adicarbonate and (C) a monohydroxy compound, followed by polymerizing theprepolymer through solid-phase or swollen solid-phasetransesterification, and the terminal hydroxyl fraction of thepolycarbonate is smaller than 15 mol %.

The terminal hydroxyl fraction of the polycarbonate is measured in thesame manner as in the above (4).

(7) In still another aspect, the polycarbonate of the invention isobtained by preparing a polycarbonate prepolymer through thermalprepolymerization of (A) an aromatic dihydroxy compound, (B) adicarbonate and (C) a poly-functional organic compound having at leastthree functional groups, followed by polymerizing the prepolymer throughsolid-phase or swollen solid-phase transesterification, and the terminalhydroxyl fraction of the polycarbonate is smaller than 15 mol %.

The terminal hydroxyl fraction of the polycarbonate is measured in thesame manner as in the above (4).

2. Method for Producing Polycarbonates of the Invention:

(1) Starting Materials

(A) Dihydroxy Compound

The starting dihydroxy compound for the component (A) includes, forexample, aromatic dihydroxy compounds and aliphatic dihydroxy compounds,and at least one selected from them may be used in the invention.

Aromatic dihydroxy compounds usable herein for the component (A) includethose of a general formula (I):

In formula (I), R³ and R⁴ each represent a halogen atom such as afluorine, chlorine, bromine or iodine atom, or an alkyl group havingfrom 1 to 8 carbon atoms such as a methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, cyclohexyl, heptylor octyl group. R³ and R⁴ may be the same or different ones. PluralR³'s, if any, may be the same or different ones; and plural R⁴'s, ifany, may be the same or different ones. m and n each represent aninteger of from 0 to 4. Z represents a single bond, an alkylene grouphaving from 1 to 8 carbon atoms, an alkylidene group having from 2 to 8carbon atoms, a cycloalkylene group having from 5 to 15 carbon atoms, acycloalkylidene group having from 5 to 15 carbon atoms, or a bond of—S—, —SO—, —SO₂—, —O— or —CO—, or a bond of the following formula (II)or (II′):

The alkylene group having from 1 to 8 carbon atoms and the alkylidenegroup having from 2 to 8 carbon atoms include, for example, methylene,ethylene, propylene, butylene, pentylene, hexylene, ethylidene andisopropylidene groups. The cycloalkylene group having from 5 to 15carbon atoms and the cycloalkylidene group having from 5 to 15 carbonatoms include, for example, cyclopentylene, cyclohexylene,cyclopentylidene and cyclohexylidene groups.

Aromatic dihydroxy compounds of formula (I) include, for example,bis(hydroxyaryl)alkanes such as bis(4-hydroxyphenyl)methane,bis(3-methyl-4-hydroxyphenyl)methane,bis(3-chloro-4-hydroxyphenyl)methane,bis(3,5-dibromo-4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,1,1-bis(2-t-butyl-4-hydroxy-3-methylphenyl)ethane,1,1-bis(2-t-butyl-4-hydroxy-3-methylphenyl)ethane,1-phenyl-1,1-bis(3-fluoro-4-hydroxy-3-methylphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane (generally referred to as bisphenol A),2,2-bis(3-methyl-4-hydroxyphenyl)propane,2,2-bis(2-methyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,1,1-bis(2-t-butyl-4-hydroxy-5-methylphenyl)propane,2,2-bis(3-chloro-4-hydroxyphenyl)propane,2,2-bis(3-fluoro-4-hydroxyphenyl)propane,2,2-bis(3-bromo-4-hydroxyphenyl)propane,2,2-bis(3,5-difluoro-4-hydroxyphenyl)propane,2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane,2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane,2,2-bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane,2,2-bis(4-hydroxy-3-bromophenyl)propane,2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3-chlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane,2,2-bis(3-bromo-4-hydroxy-5-chlorophenyl)propane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(3-methyl-4-hydroxyphenyl)butane,1,1-bis(2-butyl-4-hydroxy-5-methylphenyl)butane,1,1-bis(2-t-butyl-4-hydroxy-5-methylphenyl)butane,1,1-bis(2-t-butyl-4-hydroxy-5-methylphenyl)isobutane,1,1-bis(2-t-amyl-4-hydroxy-5-methylphenyl)butane,2,2-bis(3,5-dichloro-4-hydroxyphenyl)butane,2,2-bis(3,5-dibromo-4-hydroxyphenyl)butane,4,4-bis(4-hydroxyphenyl)heptane,1,1-bis(2-t-butyl-4-hydroxy-5-methylphenyl)heptane,2,2-bis(4-hydroxyphenyl)octane, 1,1-(4-hydroxyphenyl)ethane, etc.;bis(hydroxyaryl)cycloalkanes such as1,1-bis(4-hydroxyphenyl)cyclopentane,1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane,1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane,1,1-bis(3-phenyl-4-hydoxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)-3,5,5-trimethylcyclohexane, etc.;bis(hydroxyaryl) ethers such as bis (4-hydroxyphenyl) ether, bis(4-hydroxy-3-methylphenyl) ether, etc.; bis(hydroxyaryl)sulfides such asbis(4-hydroxyphenyl)sulfide, bis(3-methyl-4-hydroxyphenyl) sulfide,etc.; bis(hydroxyaryl)sulfoxides such as bis(4-hydroxyphenyl)sulfoxide,bis(3-methyl-4-hydroxyphenyl) sulfoxide,bis(3-phenyl-4-hydroxyphenyl)sulfoxide, etc.; bis(hydroxyaryl)sulfonessuch as bis(4-hydroxyphenyl) sulfone,bis(3-methyl-4-hydroxyphenyl)sulfone,bis(3-phenyl-4-hydroxyphenyl)sulfone, etc.; dihydroxybiphenyls such as4,4′-dihydroxybiphenyl, 4,4′-dihydroxy-2,2-dimethylbiphenyl,4,4′-dihydroxy-3,3′-dimethylbiphenyl,4,4′-dihydroxy-3,3′-dicyclohexylbiphenyl,3,3′-difluoro-4,4′-dihydroxybiphenyl, etc.

In addition to the above-mentioned compounds of formula (I), also usableherein are other aromatic dihydroxy compounds such as dihydroxybenzenes,halogen and alkyl-substituted dihydroxybenzenes, etc. For example, theyare resorcinol, 3-methylresorcinol, 3-ethylresorcinol,3-propylresorcinol, 3-butylresorcinol, 3-t-butylresorcinol,3-phenylresorcinol, 3-cumylresorcinol, 2,3,4,6-tetrafluororesorcinol,2,3,4,6-tetrabromoresorcinol, catechol, hydroquinone,3-methylhydroquinone, 3-ethylhydroquinone, 3-propylhydroquinone,3-butylhydroquinone, 3-t-butylhydroquinone, 3-phenylhydroquinone,3-cumylhydroquinone, 2,5-dichlorohydroquinone,2,3,5,6-tetramethylhydroquinone, 2,3,4,6-tetra-t-butylhydroquinone,2,3,5,6-tetrafluorohydroquinone, 2,3,5,6-tetrabromohydroquinone, etc.

Various types of aliphatic dihydroxy compounds are usable herein for thecomponent (A). For example, they include butane-1,4-diol,2,2-dimethylpropane-1,3-diol, hexane-1,6-diol, diethylene glycol,triethylene glycol, tetraethylene glycol, octaethylene glycol,dipropylene glycol, N,N-dimethyldiethanolamine, cyclohexane-1,3-diol,cyclohexane-1,4-diol, 1,4-dimethylolcyclohexane, p-xylylene glycol,2,2-bis- (4-hydroxycyclohexyl)propane, as well as ethoxylated orpropoxylated products of dihydric alcohols or phenols, such asbis-oxyethyl-bisphenol A, bis-oxyethyl-tetrachlorobisphenol A,bis-oxyethyl-tetrachlorohydroquinone, etc.

In preferred methods of producing the polymers of the invention, one ormore of the compounds mentioned above are suitably selected and used forthe dihydroxy compound component (A). Of those, preferred is bisphenolA, one of aromatic dihydroxy compounds.

Further usable herein are diesters of dihydroxy compounds, dicarbonatesof dihydroxy compounds, monocarbonates of dihydroxy compounds, etc.

Diesters of dihydroxy compounds include, for example, bisphenol Adiacetate, bisphenol A dipropionate, bisphenol A dibutyrate, bisphenol Adibenzoate, etc.

Dicarbonates of dihydroxy compounds include, for example, bisphenolAbismethyl carbonate, bisphenol Abisethyl carbonate, bisphenol Abisphenyl carbonate, etc.

Monocarbonates of dihydroxy compounds include, for example, bisphenol Amonomethyl carbonate, bisphenol A monoethyl carbonate, bisphenol Amonopropyl carbonate, bisphenol A monophenyl carbonate, etc.

Component (B)

<1> Dicarbonate:

Various types of dicarbonates are usable in the invention. For example,used is at least one selected from diaryl carbonates, dialkyl carbonatesand alkylaryl carbonates.

Diaryl carbonates usable for the component (B) include compounds of ageneral formula (III):

wherein Ar¹ and Ar² each represent an aryl group, and these may be thesame or different ones;

and compounds of a general formula (IV):

wherein Ar³ and Ar⁴ each represent an aryl group, and these may be thesame or different ones; and D¹ represents a residue of an aromaticdihydroxy compound of those mentioned above from which 2 hydroxyl groupsare removed.

Dialkyl carbonates also usable herein include compounds of a generalformula (V):

wherein R⁵ and R⁶ each represent an alkyl group having from 1 to 6carbon atoms or a cycloalkyl group having from 4 to 7 carbon atoms, andthese may be the same or different ones;

and compounds of a general formula (VI):

wherein R⁷ and R⁸ each represent an alkyl group having from 1 to 6carbon atoms or a cycloalkyl group having from 4 to 7 carbon atoms, andthese maybe the same or different ones; and D² represents a residue ofan aromatic dihydroxy compound of those mentioned above from which 2hydroxyl groups are removed.

Alkylaryl carbonates also usable herein include compounds of a generalformula (VII):

wherein Ar⁵ represents an aryl group; and R⁹ represents an alkyl grouphaving from 1 to 6 carbon atoms or a cycloalkyl group having 4 carbonatoms;

and compounds of a general formula (VIII):

wherein Ar⁶ represents an aryl group; R¹⁰ represents an alkyl grouphaving from 1 to 6 carbon atoms or a cycloalkyl group having from 4 to 7carbon atoms; and D³ represents a residue of an aromatic dihydroxycompound of those mentioned above from which 2 hydroxyl groups areremoved.

The diaryl carbonates include, for example, diphenyl carbonate, ditolylcarbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthylcarbonate, bis(diphenyl) carbonate, bisphenol A bisphenyl carbonate,etc.

The dialkyl carbonates include, for example, diethyl carbonate, dimethylcarbonate, dibutyl carbonate, dicyclohexyl carbonate, bisphenol Abismethyl carbonate, etc.

The alkylaryl carbonates include, for example, methylphenyl carbonate,ethylphenyl carbonate, butylphenyl carbonate, cyclohexylphenylcarbonate, bisphenol A methylphenyl carbonate, etc.

In the invention, one or more of the compounds mentioned above aresuitably selected and used as the dicarbonate component (B). Of those,preferred is diphenyl carbonate.

One or more of the compounds mentioned above are suitably selected andused as the dicarbonate component (B). Of those, preferred is diphenylcarbonate.

<2> Phosgene:

For the component (B) to prepare the polycarbonate prepolymer throughprepolymerization, phosgene may be used.

Component (C)

If desired, a terminating agent, a branching agent and an antioxidantmay be added to the reaction system as the starting materials inproducing the polycarbonates of the invention.

<1> Terminating Agent:

As the terminating agent, herein usable are monophenols, including, forexample, o-n-butylphenol, m-n-butylphenol, p-n-butylphenol,o-isobutylphenol, m-isobutylphenol, p-isobutylphenol, o-t-butylphenol,m-t-butylphenol, p-t-butylphenol, o-n-pentylphenol, m-n-pentylphenol,p-n-pentylphenol, o-n-hexylphenol, m-n-hexylphenol, p-n-hexylphenol,o-cyclohexylphenol, m-cyclohexylphenol, p-cyclohexylphenol,o-phenylphenol, m-phenylphenol, p-phenylphenol, o-n-nonylphenol,m-n-nonylphenol, p-n-nonylphenol, o-cumylphenol, m-cumylphenol,p-cumylphenol, o-naphthylphenol, m-naphthylphenol, p-naphthylphenol,2,6-di-t-butylphenol, 2,5-di-t-butylphenol, 2,4-di-t-butylphenol,3,5-di-t-butylphenol, 2,5-dicumylphenol, 3,5-dicumylphenol,p-tert-butylphenol, p-cumylphenol, p-phenylphenol, o,m,p-t-octylphenol,o,m,p-n-octylphenol, etc. One or more of these may be used either singlyor as combined. Of those, especially preferred are 2,6-di-t-butylphenol,2,5-di-t-butylphenol, 2,4-di-t-butylphenol, 3,5-di-t-butylphenol,2,5-dicumylphenol, 3,5-dicumylphenol, p-tert-butylphenol, p-cumylphenol,p-t-octylphenol, and p-phenylphenol.

<2> Branching Agent:

As the branching agent, herein usable are poly-functional organiccompounds having at least three functional groups. Concretely, they haveat least three functional groups of hydroxyl groups, carboxyl groups,amino groups, imino groups, formyl groups, acid halide groups,haloformate groups and the like, in one molecule, including, forexample, phloroglucinol, mellitic acid, trimellitic acid, trimelliticacid chloride, trimellitic acid anhydride, gallic acid, n-propylgallate, protocatechuic acid, pyromellitic acid, pyromellitic acidsecondary anhydride, α-resorcylic acid, β-resorcylic acid,resorcylaldehyde, trimellityl chloride, trimethyltrichloride,4-chloroformylphthalic acid anhydride, benzophenone-tetracarboxylicacid, 2,4,4′-trihydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone, 2,4,4′-trihydroxyphenyl ether, 2,2′,4,4′-tetrahydroxyphenyl ether, 2,4,4′-trihydroxydiphenyl-2-propane,2,2′-bis(2,4-dihydroxy)propane, 2,2′,4,4′-tetrahydroxydiphenylmethane,2,4,4′-trihydroxydiphenylmethane, 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl]-4- [α′,α′-bis(4″-hydroxyphenyl)ethyl]benzene, α,α′,α″-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene,2,6-bis(2′-hydroxy-5′-methylbenzyl)-4-methylphenol,4,6-dimethyl-2,4,6-tris(4′-hydroxyphenyl)-heptene-2,4,6-dimethyl-2,4,6-dimethyl-tris(4-hydroxyphenyl)-heptane-2,1,3,5-tris(4-hydroxyphenyl)benzene,1,1,1-tris (4′-hydroxyphenyl)ethane,2,2-bis[4,4-bis(4′-hydroxyphenyl)cyclohexyl]-propane,2,6-bis(2′-hydroxy-5′-isopropylbenzyl)-4-isopropylphenol,bis[2-hydroxy-3-(2′-hydroxy-5′-methylbenzyl)-5-methylphenyl]methane,bis[2-hydroxy-3-(21-hydroxy-5′-isopropylbenzyl)-5-methylphenyl]methane,tetrakis(4-hydroxyphenyl)methane, tris(4-hydroxyphenyl)phenylmethane,2′,4,7-trihydroxyflavan,2,4,4-trimethyl-2′,4′-dihydroxyphenylisopropyl)benzene,tris(4′-hydroxyaryl)-amyl-s-triazine,1-[α-methyl-α-(4′-hydroxyphenyl)ethyl]-3-[α′,α′-bis(4″-hydroxyphenyl)ethyl]benzene,isatin-bis(o-cresol), α,α,α′,α′-tetrakis(4-hydroxyphenyl)-p-xylene,α,α,α′,α′-tetrakis(3-methyl-4-hydroxyphenyl)-p-xylene,α,α,α′,α′-tetrakis (2-methyl-4-hydroxyphenyl) -p-xylene,α,α,α′,α′-tetrakis(2,5-dimethyl-4-hydroxyphenyl)-p-xylene,α,α,α′,α′-tetrakis(2,6-dimethyl-4-hydroxyphenyl)-p-xylene, α,α′-dimethyl-α,α,α′,α′-tetrakis (4-hydroxyphenyl) -p-xylene, etc. One ormore of these branching agents may be used either singly or as combined.

Above all, especially preferred are 1,1,1-tris(4-hydroxyphenyl)ethane,1,1,1-tris(4-hydroxy-3-methylphenyl)ethane,1,1,1-tris(4-hydroxy-3,5-dimethylphenyl)ethane,1,1,1-tris(3-chloro-4-hydroxyphenyl)ethane,1,1,1-tris(3,5-dichloro-4-hydroxyphenyl)ethane,1,1,1-tris(3-bromo-4-hydroxyphenyl)ethane,1,1,1-tris(3,5-dibromo-4-hydroxyphenyl)ethane,tris(4-hydroxyphenyl)methane, tris(4-hydroxy-3-methylphenyl)methane,tris(4-hydroxyphenyl-3,5-dimethylphenyl)methane,tris(3-chloro-4-hydroxyphenyl)methane,tris(3,5-dichloro-4-hydroxyphenyl)methane,tris(3-bromo-4-hydroxyphenyl)methane,tris(3,5-dibromo-4-hydroxyphenyl)methane,α,α′-dimethyl-α,α,α′,α′-tetrakis(4-hydroxyphenyl)-p-xylene, etc.

<3> Antioxidant:

Preferred are phosphorus-containing antioxidants for use herein,including, for example, trialkyl phosphates, tricycloalkyl phosphites,triaryl phosphites, monoalkyldiaryl phosphites, trialkyl phosphates,tricycloalkyl phosphates, triaryl phosphates, etc.

(2) Preparation of Prepolymer Through Prepolymerization

Prepolymers are prepared through prepolymerization of theabove-mentioned starting materials, a dihydroxy compound for thecomponent (A), a dicarbonate or phosgene for the component (B), andoptionally a terminating agent or a branching agent for the component(C). In this reaction, preferably, at least one selected fromnitrogen-containing organic basic compounds or phosphorus-containingbasic compounds is used as the polymerization catalyst. Preferredmethods and conditions for the prepolymerization are concretelydescribed hereinunder.

<1> Method of Prepolymerization:

(a) A dihydroxy compound, a dicarbonate, and optionally a terminatingagent or a branching agent are reacted under heat to give a prepolymerwhile the aromatic monohydroxy compound formed is removed. Preferably,the prepolymer prepared in the step of prepolymerization has apolymerization-average molecular weight falling between 2000 and 20000.It is desirable that the prepolymerization is effected in a melt phase.The reaction may be effected in an inert solvent, but may be effected inno solvent. The inert solvent includes, for example, aromatic compoundssuch as diphenyl ether, halogenated diphenyl ethers, benzophenone,polyphenyl ethers, dichlorobenzene, methylnaphthalene, etc.; gases suchas carbon dioxide, dinitrogen monoxide, nitrogen etc.;chlorofluorohydrocarbons; alkanes such as ethane, propane, etc.;cycloalkanes such as cyclohexane, tricyclo(5,2,10)decane, cyclooctane,cyclodecane, etc.; alkenes such as ethene, propene, etc. The ratio ofthe dihydroxy compound to the dicarbonate to be reacted therewith (thatis, the ratio of the two reactants to be fed into a reactor) varies,depending on the type of the reactants and on the reaction conditionincluding the reaction temperature and the reaction pressure. Ingeneral, the amount of the dicarbonate may fall between 0.9 and 2.5mols, preferably between 0.95 and 2.0 mols, more preferably between 0.98and 1.5 mols, relative to one mol of the dihydroxy compound. In casewhere a monohydroxy compound is used as the terminating agent or apoly-functional organic compound having at least three functional groupsis used as the branching agent, the amount of the former may fallgenerally between 0.001 and 20 mols, but preferably between 0.0025 and15 mols, more preferably between 0.005 and 10 mols, relative to one molof the dihydroxy compound, and, similarly, the amount of the latter mayfall generally between 0.001 and 20 mols, but preferably between 0.0025and 15 mols, more preferably between 0.005 and 10 mols, relative to onemol of the dihydroxy compound.

The reaction temperature, the reaction pressure and the reaction timevary, depending on the type and the amount of the starting materials andthe catalyst used, on the intended degree of polymerization of theprepolymer to be prepared, and on the other reaction conditions.Preferably, the reaction temperature falls between 50 and 350° C., morepreferably between 100 and 320° C., even more preferably between 150 and280° C.; the pressure falls preferably between 0.1 Torr and 5 kg/cm²;and the time falls preferably between 1 minute and 100 hours, morepreferably between 2 minutes and 10 hours.

In order not to discolor the prepolymer formed, it is desirable that theprepolymerization is effected at a lower possible temperature for ashorter possible period of time.

The reactor for the step of preparing the prepolymer may be any knownpolymerization reactor. The reaction may be effected in one stage or inplural stages. One reactor may be used, or plural reactors may beconnected in series or in parallel. The reaction may be effected in abatchwise process or in a continuous process, or even in theircombination.

The ratio of the terminals in the prepolymer to be produced in theprepolymerization step is preferably such that the ratio ofphenylcarbonate terminal to hydroxyl terminal falls between 1/1 and1/0.1, more preferably between 1/0.6 and 1/0.25. If the terminal ratiofalls outside the defined range, the molecular weight of the finalpolymers to be obtained will be unfavorably limited, and it will bedifficult to obtain high-molecular polymers.

In progress of the prepolymerization, an aromatic monohydroxy compoundis formed, which is a compound having a hydroxyl group bonded to thearyl group as derived from the diaryl carbonate used. Removing this fromthe reaction system promotes the reaction. For this, preferably employedis a method of effectively agitating the reaction system withintroducing an inert gas, such as nitrogen, argon, helium, carbondioxide or the like, or a lower hydrocarbon gas into the system, therebyto remove the aromatic monohydroxy compound along with the gas; a methodof effecting the reaction under reduced pressure; or a combination ofthese methods.

(b) An aromatic dihydroxy compound may be reacted with phosgene in aknown manner to prepare a prepolymer.

<2> Catalyst for Prepolymerization:

As the catalyst for prepolymerization, preferably used arenitrogen-containing, organic basic compounds. The nitrogen-containing,organic basic compounds are not specifically defined, including, forexample, aliphatic tertiary amine compounds, aromatic tertiary aminecompounds, nitrogen-containing heterocyclic compounds, etc.

Also employable are quaternary ammonium salts of a general formula (IX):

(NR¹¹ ₄)⁺(X¹)⁻  (IX).

In formula (IX), R¹¹ represents an organic group, for example, an alkylor cycloalkyl group such as a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, an octyl group, acyclohexyl group, etc.; an aryl group such as a phenyl group, a tolylgroup, a naphthyl group, a biphenyl group, etc.; or an arylalkyl groupsuch as a benzyl group, etc. Four R¹'s may be the same or differentones; and two of them may be bonded to each other to form a cyclicstructure. X¹ represents a halogen atom, a hydroxyl group, or BR₄, inwhich R represents a hydrogen atom, or a hydrocarbon group such as analkyl group, an aryl group or the like, and four R's maybe the same ordifferent ones. Examples of the quaternary ammonium salts includeammonium hydroxides having alkyl, aryl and/or alaryl groups, such astetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, etc.;and basic salts such as tetramethylammonium borohydride,tetrabutylammonium borohydride, tetrabutylammonium tetraphenyl borate,tetramethylammonium tetraphenyl borate, etc.

Of the nitrogen-containing, organic basic compounds noted above,preferred are the quaternary ammonium salts of formula (I), concretelysuch as tetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetramethylammonium borohydride, and tetrabutylammonium borohydride,since they have high catalytic activity and since they are easilypyrolyzed and hardly remain in the polymers produced. Of those,especially preferred is tetramethylammonium hydroxide.

One or more of these nitrogen-containing, organic basic compounds areemployable herein either singly or as combined.

It is desirable to use the nitrogen-containing, organic basic compoundin an amount of from 10⁻⁸ to 10⁻² mols, more preferably from 10⁻⁷ to10⁻³ mols. If the amount of the nitrogen-containing, organic basiccompound used is smaller than 10⁻⁸ mols, it is unfavorable since thecatalytic activity in the initial stage of the reaction will be low; butif larger than 10⁻² mols, it is also unfavorable since the cost of thecatalyst increases.

<3> Crystallization of Prepolymer:

The prepolymer may be crystallized, for which the method is notspecifically defined. To crystallize it, preferably, the prepolymer isprocessed in solvents or under heat. In the former solvent method, theprepolymer is crystallized in suitable solvents. The solvents includechloromethane, methylene chloride, chloroform, etc. The amount of thesolvent to be used varies, depending on different conditions employed,but preferably falls between 0.05 and 100 times, more preferably between0.1 and 50 times the weight of the prepolymer.

The other method of crystallization under heat is to crystallize theprepolymer by heating it at a temperature not lower than the glasstransition temperature of the intended final product, aromaticpolycarbonate, but lower than the temperature at which the prepolymerbegins to melt. The temperature Tc (° C.) at which the prepolymer iscrystallized under heat is not specifically defined, so far as it is notlower than the glass transition temperature of the intended finalproduct, aromatic polycarbonate copolymer, but lower than the meltingtemperature Tm (° C.) of the prepolymer.

(3) Production of Polycarbonate Through Polymerization

To produce the polycarbonates of the invention, preferably, apolycarbonate prepolymer is first prepared, and it is polymerized in asolid or swollen solid phase or in a thin film melt phase in thepresence of a quaternary phosphonium salt serving as a polymerizationcatalyst.

<1> Quaternary phosphonium salt:

The quaternary phosphonium salt is not specifically defined, and may beany and every one. For example, preferably used are compounds of thefollowing general formula (IX) or (X):

(PR¹² ₄)⁺(x²)⁻  (X)

(PR¹² ₄)₂ ⁺(y¹)²⁻  (XI).

In formulae (X) and (XI), R¹² represents an organic group. The organicgroup includes, for example, alkyl and cycloalkyl groups such as amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, an octyl group, a cyclohexyl group, etc.; an arylgroup such as a phenyl group, a tolyl group, a naphthyl group, abiphenyl group, etc.; and an arylalkyl group such as a benzyl group,etc. Four R¹²'s may be the same or different ones, or two of them may bebonded to each other to form a cyclic structure. X²represents a groupcapable of forming a mono-valent anion, such as a halogen atom, ahydroxyl group, an alkyloxy group, an aryloxy group, R′COO, HCO₃,(R′O)₂P(═O)O, BR″4 or the like. In those, R′ represents a hydrocarbongroup such as an alkyl group, an aryl group or the like, and two (R′O)smay be the same or different ones. R″ represents a hydrogen atom, or ahydrocarbon group such as an alkyl group, an aryl group or the like, andfour R″s may be the same or different ones. Y¹ represents a groupcapable of forming a di-valent anion, such as CO₃ or the like.

The quaternary phosphonium salts include, for example, tetra(aryl oralkyl)phosphonium hydroxides such as tetraphenylphosphonium hydroxide,tetranaphthylphosphonium hydroxide, tetra(chlorophenyl)phosphoniumhydroxide, tetra(biphenyl)phosphonium hydroxide, tetratolylphosphoniumhydroxide, tetramethylphosphonium hydroxide, tetraethylphosphoniumhydroxide, tetrabutylphosphonium hydroxide, etc.; as well astetramethylphosphonium tetraphenyl borate, tetraphenylphosphoniumbromide, tetraphenylphosphonium phenolate, tetraphenylphosphoniumtetraphenyl borate, methyltriphenylphosphonium tetraphenyl borate,benzyltriphenylphosphonium tetraphenyl borate,biphenyltriphenylphosphonium tetraphenyl borate, tetratolylphosphoniumtetraphenyl borate, tetraphenylphosphonium phenolate, tetra(p-t-butylphenylyphosphonium diphenyl phosphate,triphenylbutylphosphonium phenolate, triphenylbutylphosphoniumtetraphenyl borate, etc.

Of the quaternary phosphonium salts noted above, preferred are thosehaving alkyl groups, since they have high catalytic activity and sincethey are easily pyrolyzed and hardly remain in the polymers produced.For example, preferably used are tetramethylphosphonium methyltriphenylborate, tetraethylphosphonium ethyltriphenyl borate,tetrapropylphosphonium propyltriphenyl borate, tetrabutylphosphoniumbutyltriphenyl borate, tetrabutylphosphonium tetraphenyl borate,tetraethylphosphonium tetraphenyl borate, trimethylethylphosphoniumtrimethylphenyl borate, trimethylbenzylphosphonium benzyltriphenylborate, etc.

Also preferred are tetraalkylphosphonium salts such astetramethylphosphonium hydroxide, tetraethylphosphonium hydroxide,tetrabutylphosphonium hydroxide and others, as their decompositiontemperature is relatively low and they are readily decomposed notremaining as impurities in the products, polycarbonates. In addition,since the number of carbon atoms constituting them is small, the scaleof the unit batch for producing polycarbonates can be reduced.Therefore, they are preferred, as having the advantage of low productioncosts.

Except the compounds of formulae (X) and (XI) mentioned above, alsousable herein are bis-tetraphenylphosphonium salt of2,2-bis(4-hydroxyphenyl)propane, and ethylenebis(triphenylphosphonium)dibromide, trimethylenebis(triphenylphosphonium)-bis(tetraphenylborate), etc.

Further usable are quaternary phosphonium salts having aryl groupsand/or branched alkyl groups. For example, they are compounds of ageneral formula (XI):

(R¹³ _(n)PR¹⁴ _(4−n))⁺(X²)⁻  (XII),

or compounds of a general formula (XII):

(R¹³ _(n) PR ¹⁴ _(4−n))⁺2(y¹)²⁻  (XIII).

In formulae (XII) and (XIII);

n represents an integer of from 1 to 4.

R¹³ represents at least one selected from an aryl group and a branchedalkyl group. The branched alkyl group has a structure of “R₃C—”, inwhich R represents at least one selected from a hydrogen atom, an alkylgroup, a substituted alkyl group, an aryl group, and a substituted arylgroup, and at least two of the three R′s may be bonded to each other toform a cyclic structure. In this, however, two R′s must not be hydrogensat the same time. For example, it includes a cycloalkyl group, abranched alkyl group such as an isopropyl group, a tert-butyl group,etc., or an arylalkyl group such as a benzyl group, etc. When n is 2 ormore, plural R′s maybe the same or different ones.

R¹⁴ represents an alkyl group, a substituted alkyl group, an aryl group,or a substituted aryl group.

X² represents a group capable of forming a mono-valent anion, such as ahalogen atom, a hydroxyl group, an alkyloxy group, an aryloxy group,R′COO, HCO₃, (R′O)₂P(═O)O, BR″₄ or the like. In those, R′ represents ahydrocarbon group such as an alkyl group, an aryl group or the like, andtwo (R′O)s may be the same or different ones. R″ represents a hydrogenatom, or a hydrocarbon group such as an alkyl group, an aryl group orthe like, and four R″s may be the same or different ones.

Y¹ represents a group capable of forming a di-valent anion, such as CO₃or the like.

The quaternary phosphonium salts include, for example, tetra(aryl oralkyl)phosphonium hydroxides, such as tetraphenylphosphonium hydroxide,tetranaphthylphosphonium hydroxide, tetra(chlorophenyl)phosphoniumhydroxide, tetra(biphenyl)phosphonium hydroxide, tetratolylphosphoniumhydroxide, tetrahexylphosphonium hydroxide, etc.; mono(aryl oralkyl)triphenylphosphonium hydroxides, such asmethyltriphenylphosphonium hydroxide, ethyltriphenylphosphoniumhydroxide, propyltriphenylphosphonium hydroxide,butyltriphenylphosphonium hydroxide, octyltriphenylphosphoniumhydroxide, tetradecyltriphenylphosphonium hydroxide,benzyltriphenylphosphonium hydroxide, ethoxybenzyltriphenylphosphoniumhydroxide, methoxymethyltriphenylphosphonium hydroxide,acetoxymethyltriphenylphosphonium hydroxide,phenacyltriphenylphosphonium hydroxide, chloromethyltriphenylphosphoniumhydroxide, bromomethyltriphenylphosphonium hydroxide,biphenyltriphenylphosphonium hydroxide, naphtyltriphenylphosphoniumhydroxide, chlorophenyltriphenylphosphonium hydroxide,phenoxyphenyltriphenylphosphonium hydroxide,methoxyphenyltriphenylphosphonium hydroxide,acetoxyphenyltriphenylphosphonium hydroxide,naphtylphenyltriphenylphosphonium hydroxide, etc.;mono(aryl)trialkylphosphonium hydroxides, such asphenyltrimethylphosphonium hydroxide, biphenyltrimethylphosphoniumhydroxide, phenyltrihexylphosphonium hydroxide,biphenyltrihexylphosphonium hydroxide, etc.; diaryldialkylphosphoniumhydroxides, such as dimethyldiphenylphosphonium hydroxide,diethyldiphenylphosphonium hydroxide, di(biphenyl)diphenylphosphoniumhydroxide, etc.; tetraarylphosphonium tetraphenyl borates, such astetraphenylphosphonium tetraphenyl borate, tetranaphthylphosphoniumtetraphenyl borate, tetra(chlorophenyl)phosphonium tetraphenyl borate,tetra(biphenyl)phosphonium tetraphenyl borate, tetratolyiphosphoniumtetraphenyl borate, etc.; mono(aryl or alkyl)triphenylphosphoniumtetraphenyl borates, such as methyltriphenylphosphonium tetraphenylborate, ethyltriphenylphosphonium tetraphenyl borate,propyltriphenylphosphonium tetraphenyl borate, butyltriphenylphosphoniumtetraphenyl borate, octyltriphenylphosphonium tetraphenyl borate,tetradecyltriphenylphosphonium tetraphenyl borate,benzyltriphenylphosphonium tetraphenyl borate,ethoxybenzyltriphenylphosphonium tetraphenyl borate,methoxymethyltriphenylphosphonium tetraphenyl borate,acetoxymethyltriphenylphosphonium tetraphenyl borate,phenacyltriphenylphosphonium tetraphenyl borate,chloromethyltriphenylphosphonium tetraphenyl borate,bromomethyltriphenylphosphonium tetraphenyl borate,biphenyltriphenylphosphonium tetraphenyl borate,naphtyltriphenylphosphonium tetraphenyl borate,chlorophenyltriphenylphosphonium tetraphenyl borate,phenoxyphenyltriphenylphosphonium tetraphenyl borate,acetoxyphenyltriphenylphosphonium tetraphenyl borate,naphthylphenyltriphenylphosphonium tetraphenyl borate, etc.;monoaryltrialkylphosphonium tetraphenyl borates, such asphenyltrimethylphosphonium tetraphenyl borate,biphenyltrimethylphosphonium tetraphenyl borate,phenyltrihexylphosphonium tetraphenyl borate,biphenyltrihexylphosphonium tetraphenyl borate, etc.;diaryldialkylphosphonium tetraphenyl borates, such asdimethyldiphenylphosphonium tetraphenyl borate,diethyldiphenylphosphonium tetraphenyl borate,di(biphenyl)diphenylphosphonium tetraphenyl borate, etc.

In these quaternary phosphonium salts, the counter anion, hydroxide ortetraphenyl borate, may be replaced with any of an aryloxy group such asphenoxide, etc., an alkyloxy group such as methoxide, ethoxide, etc., analkylcarbonyloxy group such as acetate, etc., an arylcarbonyloxy groupsuch as benzoate, etc., ahalogenatomsuch as chloride, bromide, etc., andthese derivatives are also employable herein.

Apart from the compounds of formula (XII), also employable herein arecompounds of formula (XIII) having a di-valent counter anion. As those,for example, mentioned are quaternary phosphonium salts such asbis(tetraphenylphosphonium) carbonate, bis(biphenyltriphenylphosphonium)carbonate, etc., as well as bis-tetraphenylphosphonium salt of2,2-bis(4-hydroxyphenyl)propane, and ethylenebis(triphenylphosphonium)dibromide, trimethylenebis(triphenylphosphonium) bis-(tetraphenylborate), etc.

In addition, further employable herein are compounds of general formulae(XIV) and (XV):

((R¹⁵—Ph)_(n)—PPh_((4−n)))⁺(X³)⁻  (XIV)

 ((R¹⁵—Ph)_(n)—PPh_((4−n)))₂ ⁺(y²)²⁻  (XV)

wherein R¹⁵ represents an organic group, and plural R¹⁵'s, if any, maybe the same or different ones; X³ represents a halogen atom, a hydroxylgroup, an alkyloxy group, an aryloxy group, an alkylcarbonyloxy group,an arylcarbonyloxy group, HCO₃, or BR₄ (in which R represents a hydrogenatom or a hydrocarbon group, and four R′s may be the same or differentones); Ph represents a phenyl group; y² represents CO₃; and n representsan integer of from 1 to 4.

Specific examples of those quaternary phosphonium compounds include, forexample, tetraphenylphosphonium hydroxide, biphenyltriphenylphosphoniumhydroxide, methoxyphenyltriphenylphosphonium hydroxide,phenoxyphenyltriphenylphosphonium hydroxide,naphthylphenyltriphenylphosphonium hydroxide, tetraphenylphosphoniumtetraphenyl borate, biphenyltriphenylphosphonium tetraphenyl borate,methoxyphenyltriphenylphosphonium tetraphenyl borate,phenoxyphenyltriphenylphosphonium tetraphenyl borate,naphthylphenyltriphenylphosphonium tetraphenyl borate,tetraphenylphosphonium phenoxide, biphenyltriphenylphosphoniumphenoxide, methoxyphenyltriphenylphosphonium phenoxide,phenoxyphenyltriphenylphosphonium phenoxide,naphthylphenyltriphenylphosphonium phenoxide, tetraphenylphosphoniumchloride, biphenyltriphenylphosphonium chloride,methoxyphenyltriphenylphosphonium chloride,phenoxyphenyltriphenylphosphonium chloride,naphthylphenyltriphenylphosphonium chloride, etc. Of those quaternaryphosphonium salts, preferred is tetraphenylphosphonium tetraphenylborate in view of the balance between the catalytic activity of thecompound and the Equality of the polycarbonates produced.

Specific examples of branched alkyl-having quaternary phosphonium saltsinclude isopropyltrimethylphopshonium, isopropyltriethylphosphonium,isopropyltributylphosphonium, isopropyltriphenylphosphonium,tetraisopropylphosphonium, cyclohexyltriethylphosphonium,cyclohexyltrimethylphosphonium, cyclohexyltributylphosphonium,cyclohexyltriphenylphosphonium, tetracyclohexylphosphonium,1,1,1-triphenylmethyltrimethylphosphonium,1,1,1-triphenylmethyltriethylphosphonium,1,1,1-triphenylmethyltributylphosphonium,1,1,1-triphenylmethyltriphenylphosphonium, etc.

Specific examples of counter anions for X³ include hydroxide,borohydride, tetraphenyl borate, acetate, propionate, fluoride,chloride, hydrocarbonate, etc.

One example of y² is carbonate.

As specific examples of salts composed of a branched alkyl-havingquaternary phosphonium (cation) and X or Y (anion), mentioned arevarious combinations of the specific examples for cations and anionsnoted above. For those, specifically mentioned areisopropyltrimethylphosphonium hydroxide, cyclohexyltriphenylphosphoniumchloride, 1,1,1-triphenylmethyltriethylphosphonium acetate,bis(isopropyltriethylphosphonium) carbonate, etc.

Of those branched alkyl-having quaternary phosphonium salts, especiallypreferred are cyclohexyltriphenylphosphonium tetraphenyl borate andcyclopentyltriphenylphosphonium tetraphenyl borate, since theircatalytic activity and the quality of polycarbonates produced are wellbalanced.

Also mentioned for use herein are carboxylates such astetramethylpnosphonium acetate, tetraethylphosphonium acetate,tetrapropylphosphonium acetate, tetrabutylphosphonium acetate,tetrapentylphosphonium acetate, tetrahexylphosphonium acetate,tetraheptylphosphonium acetate, tetraoctylphosphonium acetate,tetradecylphosphonium acetate, tetradodecylphosphonium acetate,tetratolylphosphonium acetate, tetraphenylphosphonium acetate,tetramethylphosphonium benzoate, tetraethylphosphonium benzoate,tetrapropylphosphonium benzoate, tetraphenylphosphonium benzoate,tetramethylphosphonium formate, tetraethylphosphonium formate,tetrapropylphosphonium formate, tetraphenylphosphonium formate,tetramethylphosphonium propionate, tetraethylphosphonium propionate,tetrapropylphosphonium propionate, tetramethylphosphonium butyrate,tetraethylphosphonium butyrate, tetrapropylphosphonium butyrate, etc.

It is desirable that the amount of metallic impurities in the quaternaryphosphonium salts for use in the invention is as small as possible.Especially preferably, the amount of alkali metal and alkaline earthmetal compounds in those salts is not larger than 50 ppm.

It is desirable to use the quaternary phosphonium salt in an amount offrom 10⁻⁸ to 10⁻² mols relative to one mol of the starting dihydroxycompound for the component (A). If the amount of the quaternaryphosphonium salt used is smaller than 10⁻⁸ mols, it is unfavorable sincethe catalytic activity in the initial stage of the reaction will be low;but if larger than 10⁻² mols, it is also unfavorable since the cost ofthe catalyst increases.

<2> Solid-phase Polymerization:

The crystallized solid prepolymer is polymerized in the presence of aquaternary phosphonium salt serving as a catalyst. In this case, theside products, aromatic monohydroxy compound and/or diaryl carbonate areremoved from the reaction system, whereby the reaction is accelerated.For this, for example, preferably employed is a method of introducing aninert gas such as nitrogen, argon, helium, carbon dioxide or the like,or a hydrocarbon gas or a poor solvent gas into the reaction system tothereby remove the side products together with the gas, a method ofeffecting the reaction under reduced pressure, or a combination of thetwo. In the method of introducing the gas for accompanying the sideproducts, it is desirable that the gas is pre-heated at a temperaturenear to the reaction temperature.

For the condition of the poor solvent usable herein, the solubility ofthe final product, polycarbonate in the solvent shall be at most 0.1% byweight under the reaction condition mentioned below, and the solventshall have little influence on the reaction. Preferably, the poorsolvent is a linear or branched, saturated hydrocarbon compound havingfrom 4 to 18 carbon atom, or an unsaturated hydrocarbon compound havingfrom 4 to 18 carbon atoms in which the degree of unsaturation is low.Its boiling point is preferably not higher than 250° C. If higher than250° C., the remaining solvent will be difficult to remove, and thequality of the product will be poor.

The shape of the crystallized prepolymer to be subjected to solid-phasepolymerization is not specifically defined, but the prepolymer ispreferably in the form of pellets, beads or the like.

The reaction catalyst for solid-phase polymerization is preferably aquaternary phosphonium salt, but may be any other catalyst. The catalysthaving been added to the system in the step of preparing the prepolymer,and still remaining therein could act, as it would be, also in the stepof solid-phase polymerization, or the catalyst mentioned above may beadded to the system. The additional catalyst may be powder, liquid orgaseous.

The reaction temperature, Tp (° C.), and the reaction time forsolid-phase polymerization shall vary, depending on the type (includingthe chemical structure, the molecular weight) and the shape of thecrystallized prepolymer, the presence or absence of the catalyst in thecrystallized prepolymer, the type and the amount of the catalysttherein, the type and the amount of an additional catalyst that may beoptionally added to the system, the degree of crystallization of thecrystallized prepolymer, the melting temperature Tm′ (° C.) of thecrystallized prepolymer, the necessary degree of polymerization of theintended final product, aromatic polycarbonate copolymer, and otherreaction conditions. Concretely, it is desirable that the prepolymer ispolymerized in a solid phase while being heated at a temperature notlower than the glass transition temperature of the intended finalproduct, aromatic polycarbonate copolymer and falling within the rangewithin which the crystallized prepolymer being polymerized does not meltbut could be all the time in a solid phase, more preferably fallingwithin the range to be indicated by the following formula:

Tm′−50≦Tp<Tm′  (XVI),

for 1 minute to 100 hours, more preferably for 0.1 to 50 hours or so.

For example, when a polycarbonate of bisphenol A is produced, thetemperature range is preferably from about 150 to 260° C., morepreferably from about 180 to 245° C.

In the polymerization step, the system is preferably agitated in orderthat the prepolymer being polymerized could be heated as uniformly aspossible and that the side products could be removed from the system assmoothly as possible. For this, for example, the system is stirred, orthe reactor is rotated, or the system is fluidized with hot gas.

In general, aromatic polycarbonates favorable to industrial use have aweight-average molecular weight of from 6000 to 200000 or so. In thesolid-phase polymerization step as herein, polycarbonates having adegree of polymerization within that range are easy to produce.

The degree of crystallization of the aromatic polycarbonate to beobtained through solid-phase polymerization of the crystallizedprepolymer is generally larger than that of the starting prepolymer.Therefore, the product obtained in the method of the invention isgenerally a crystalline, aromatic polycarbonate powder. The crystallinearomatic polycarbonate powder thus produced could be directly pelletizedin an extruder, without being cooled, or could be directly molded in amolding machine also without being cooled. The ratio of the degree ofprepolymerization which has some influence on the subsequentpolymerization, to that of solid-phase polymerization may be varied in abroad range.

<3> Swollen Solid-phase Polymerization:

The prepolymer having been prepared in the prepolymerization step iscrystallized, and then further polymerized in a solid phase while beingswollen with a swelling gas. The swelling gas to be used herein ismentioned below. Swollen solid-phase polymerization is combined withtransesterification to give the intended polycarbonates, in which theside products, low-molecular compounds such as phenols are removedthrough evaporation or extraction. For this, the low-molecular compoundsare evaporated away or extracted out, while being separated from thehigh-molecular compound (prepolymer) having been swollen with a swellinggas introduced into the system. This is based on the principle that theremoval of low-molecular compounds from swollen prepolymers throughevaporation or extraction is more effective than that fromhigh-viscosity prepolymer melts or from crystallized solid prepolymers,as the substance mobility rate is higher and the reaction efficiency ishigher in the former than in the latter.

The swollen solid-phase polymerization method includes a step of flakingthe prepolymer prepared in the previous step, and a step of furtherpolymerizing the prepolymer to give a polymer having a higher molecularweight, through solid-phase polymerization in the presence of a swellingsolvent stream (swollen solid-phase polymerization step).

The prepolymer favorable to the flaking step has a molecular weightfalling between 2000 and 20000 in terms of the viscosity-averagemolecular weight (Mv). Prepolymers having a molecular weight lower thanthe defined range shall have a low melting point, for which thesolid-phase polymerization temperature must be lowered. Therefore, suchlow-molecular prepolymers are unfavorable, as their reaction speed islow.

For flaking the prepolymer, any known method is employable. For example,employable case by case is any of rotary granulation, extrusiongranulation, compression granulation, melting granulation, spray-dryinggranulation, fluidized-bed granulation, grinding granulation, stirringgranulation, liquid-phase granulation, vacuum-freezing granulation, etc.

The shape of the prepolymer flakes is not specifically defined. In viewof their easy handlability, preferred are pellets, beads and the like.To prepare the prepolymer flakes, effectively employed is a stirringgranulation method that comprises once dissolving the prepolymer in aswelling solvent necessary in the next step, followed by flaking itwhile the prepolymer solution is mixed with a poor solvent for theintended product, polycarbonate. Prior to being polymerized, theprepolymer flakes do not need drying.

The swelling solvent to be used herein is meant to include singlesolvents capable of swelling polycarbonates by themselves under thereaction conditions that will be mentioned below; mixtures of suchsolvents; and mixtures to be prepared by adding one or more of poorsolvents for polycarbonates to the single solvents or their mixtures.The swollen condition in this step is meant to indicate that thestarting prepolymer flakes are swollen by volume or weight at least to adegree not lower than the thermal swell thereof under the reactionconditions to be mentioned below. The swelling solvent is a singlecompound having a boiling point at which it can completely vaporizewithin the range of the following reaction conditions or having a vaporpressure of generally not lower than 50 Torr under those reactionconditions, or a mixture of such compounds, and it can form the swollencondition defined above.

The swelling solvent for use herein is not specifically defined, so faras it satisfies the swelling conditions noted above. For example,aromatic compounds and oxygen-containing compounds having a solubilityparameter of generally from 4 to 20 (cal/cm³)^(½), preferably from 4 to14 (cal/cm³)^(½) belong to the category of the swelling solvent.Concretely, the swelling solvent for use in the invention includes, forexample, aromatic hydrocarbons such as benzene, toluene, xylene,ethylbenzene, diethylbenzene, propylbenzene, dipropylbenzene, etc.;ethers such as tetrahydrofuran, dioxane, etc.; ketones such as methylethyl ketone, methyl isobutyl ketone, etc. Of those, preferred aresingle compounds of aromatic hydrocarbons having from 6 to 20 carbonatoms, and their mixtures.

Regarding its conditions, the poor solvent to be mixed with the swellingsolvent shall be such that the solubility of the product, polycarbonatein it is at most 0.1% by weight under the reaction conditions to bementioned below and that it participates little in the reaction.Preferred examples of the poor solvent are linear or branched, saturatedhydrocarbon compounds having from 4 to 18 carbon atoms, or hydrocarboncompounds unsaturated to a low degree and having from 4 to 18 carbonatoms. If the boiling point of the swelling solvent and that of the poorsolvent are both above 250° C., it is unfavorable since the remainingsolvents will be difficult to remove from the product, polycarbonate andthe quality of the product will be poor.

Where a mixture of the poor solvent and the swelling solvent is usedherein, the proportion of the swelling solvent shall be at least 1% byweight of the mixed solvent, but preferably at least 5% by weightthereof.

In the swollen solid-phase polymerization step, the reaction temperaturepreferably falls between 100 and 240° C., and the reaction pressurepreferably falls between 10 Torr and 5 kg/cm²G, but is more preferablynot higher than the atmospheric pressure. If the reaction temperature islower than the defined range, the prepolymer could not undergotransesterification. On the other hand, however, if the reaction iseffected at high-temperature conditions exceeding the melting point ofthe prepolymer, the reaction system could not keep a solid phase, andthe prepolymer particles will fuse together at such high temperatures.If so, the operability to continue the reaction will be greatly lowered.Therefore, the reaction temperature must not be higher than the meltingpoint of the prepolymer.

As the reaction catalyst in the swollen solid-phase polymerization step,used are a quaternary phosphonium salt and optionally any othercatalyst. The reaction catalyst having been added to and still remainingin the prepolymerization system could act, as it would be, further inthe swollen solid-phase polymerization step, but, as the case maybe, anadditional catalyst such as that mentioned above may be added to theswollen solid-phase polymerization system. The additional catalyst maybe powdery, liquid or gaseous.

Regarding the mode of feeding the swelling solvent gas into thepolymerization system, the liquid solvent may be directly fed into thereactor and is vaporized therein; or the liquid solvent is, after havingbeen previously vaporized by the use of a heat exchanger or the like,fed into the reactor. The flow rate of the swelling gas solvent may beat least 1×10⁻³ cm/sec, but is preferably at least 1×10⁻³ cm/sec. Theamount of the swelling gas to be fed into the reactor is preferably atleast 0.5 liters (ground state)/hr/g of prepolymer. The flow rate of theswelling gas solvent is closely related with the reaction rate. Theswelling gas solvent acts to remove phenols and serves as a heat medium,and the reaction rate increases with the increase in the gas flow rate.The reactor to be used herein for such swollen solid-phasepolymerization is not specifically defined.

The polycarbonate of which the molecular weight has been increased inthe manner as above may be dried and pelletized in any known manner withno limitation. When additives such as those mentioned above are added tothe polycarbonate, some preferred methods are employed; for example,additive powder may be directly added to the flaky polymer productbefore or after the product is dried; or additive liquid may be sprayedover the product; or additive vapor may be applied thereto so that theproduct could absorb it. Apart from the methods, additives may be addedto the polymer product in an extruder before the product is pelletized.

The blend ratio of the inert gas to the swelling solvent may be suchthat the swelling solvent accounts for at least 1% by volume of themixed solvent gas, but preferably at least 5% by volume thereof.

<4> Oxygen Concentration and Water Concentration in Vapor-phasePolymerization System:

In the invention, the oxygen concentration in the vapor phase in thepolymerization reaction system must be at most 2 ppm, but is preferablyat most 1 ppm, more preferably at most 0.5 ppm. It is desirable that thewater concentration in the reaction system is at most 2 ppm, morepreferably at most 1 ppm. If the oxygen concentration in thepolymerization reaction system is larger than 2 ppm, the resins to beobtained will be often discolored and their thermal stability is poor.On the other hand, if the water concentration therein is larger than 2ppm, it is undesirable since the polymers being produced will behydrolyzed and since too much water will have some negative influenceson the activity of the catalyst being used.

The method for lowering the oxygen concentration in the reaction systemto be at most 2 ppm and for lowering the water concentration thereinalso to be at most 2 ppm is not specifically defined. For example, anoxygen-removing duct equipped with an oxygen filter or the like and awater-removing duct equipped with a moisture filter or the like may bedisposed before the polymerization reactor in the production line.

<5> Thin Film Melt-phase Polymerization:

The polycarbonate prepolymer mentioned above may be put into apolymerization reactor equipped with heating, pressure-reducing and meltfilm-forming units, in which the prepolymer may be polymerized into apolymer having an increased molecular weight while it is melted to forma thin melt film by driving the pressure-reducing unit. This method isreferred to as a thin-film polymerization method. In the method, thetransesterification of the prepolymer is much promoted to give a polymerhaving an increased molecular weight. In the method, in general, theprepolymer in melt forms a thin melt film having a thickness of at most5 mm, preferably at most 3 mm, more preferably at most 1 mm in thepresence of a catalyst such as the above-mentioned quaternaryphosphonium salt or the like, and undergoes transesterification at areaction temperature falling between 50 and 320° C., preferably between100 and 320° C., more preferably between 150 and 280° C., under areaction pressure falling between 0.1 Torr and 5 kg/cm²G, for a reactionperiod of time falling between 1 minute and 100 hours, preferablybetween 2 and 20 hours.

Forming the thin melt film of the prepolymer is not specificallydefined, for which, for example, employed is the method mentionedhereinabove in the section of <1> prepolymerization. Briefly, theprepolymer is dissolved in the solvent mentioned above, then theresulting solution is spread over the bottom of the reactor having abroad bottom area, and the solvent is evaporated away under heat to givea thin melt film of the prepolymer.

The thin-film polymerization method is one particular method of knownmelt transesterification methods, and it is targeted to acceleratingphenol vapor removal to promote the reaction. Another advantage of themethod is that the polymer produced is prevented as much as possiblefrom being degraded by the released phenol to thereby attain the objectof the invention which is to reduce the impurities in thepolycarbonates.

The polycarbonates of the invention may be mixed with any knownadditives of, for example, plasticizers, pigments, lubricating agents,mold-releasing agents, stabilizers, inorganic fillers, etc., before theyare used. The polycarbonates may be blended with any other polymers,such as polyolefins, polystyrenes, polyesters, polysulfonates,polyamides, polyphenylene ethers, etc. In particular, they areeffectively blended with polyphenylene ethers, polyether nitriles,terminal-modified polysiloxane compounds, modified polypropylenes,modified polystyrenes and the like having OH, COOH, NH₂ or the likegroup at their terminals.

3. Optical Materials and Others Containing Polycarbonate

In the polycarbonates of the invention, the monomers remaining thereinare reduced. Therefore, the polycarbonates are not yellowed and theirmolecular weight and physical properties are not degraded. Accordingly,the polycarbonates are extremely favorable to optical materials.

In the invention, a terminating agent such as cumylphenol or the like isoptionally used in producing the polycarbonates. In ordinary meltpolymerization, such a terminating agent is difficult to use, andpolycarbonate molecules could be hardly terminated with it. However, inthe invention, the polycarbonates can be easily terminated even withsuch a terminating agent in solid-phase or swollen solid-phasepolymerization. As will be known, the physical properties including thelow-temperature impact resistance of the polycarbonates of the inventionare improved, in addition to the above-mentioned improvements, and thepolycarbonates are useful as optical materials.

In producing the polycarbonates of the invention, optionally used is abranching agent. As will be known, the physical properties including themelt tension of the polycarbonates are improved, in addition to theabove-mentioned improvements, and the polycarbonates are useful as blowmolding materials.

EXAMPLES

The invention is described in more detail with reference to thefollowing Examples and Comparative Examples, which, however, are notintended to restrict the scope of the invention.

Example 1

228 g (1.0 mol) of bisphenol A (BPA), 246 g (1.15 mols) of diphenylcarbonate (DPC) and 0.5 mmols of tetramethylammonium hydroxide (TMAH)were put into a one liter nickel steel autoclave equipped with astirrer, and purged with argon five times in all. Next, the mixture washeated at 190° C. and reacted for 30 minutes in the argon atmosphere.Next, this was further heated gradually up to 235° C. and reacted for 60minutes while being degassed up to a vacuum degree of 60 Torr; then thiswas still further heated gradually up to 270° C. and reacted for 120minutes while being degassed up to a vacuum degree of 10 Torr; and thiswas still further reacted for 30 minutes while being degassed up to avacuum degree of 1 Torr and then for 30 minutes while being degassed upto a vacuum degree of 0.5 Torr all at the same temperature of 270° C.After having been thus reacted, the system in the reactor was purgedwith argon to have an atmospheric pressure, and the prepolymer thusformed was taken out and ground.

The viscosity-average molecular weight of the prepolymer was 7200, andthe terminal hydroxyl fraction thereof was 30%.

The prepolymer was dissolved in methylene chloride along with 10⁻⁵ molsof cyclohexyltriphenylphosphonium tetraphenyl borate (HPTB) serving as acatalyst, to which was added n-heptane so as to deposit the prepolymer.After concentrated to be solid, this was dried in vacuum to obtain apowder of the prepolymer. 9 g of the powder was put into a SUS tubehaving a diameter of 10 mm and a length of 200 mm, into which wasintroduced nitrogen gas at a flow rate of 100 ml/min. In that condition,this was heated from room temperature up to 240° C., and polymerized ina solid phase for 4 hours to obtain a polycarbonate. Its data are givenin Table 1.

Example 2

The same process as in Example 1 was repeated, except that heptane gaswas introduced into the solid-phase polymerization system. The data ofthe polycarbonate thus produced herein are given in Table 1.

Example 3

8.04 g of the prepolymer prepared in Example 1 was put on a SUSlaboratory dish having a diameter of 32 cm, to which was added 10 ml ofmethylene chloride. On the dish, the prepolymer was dissolved inmethylene chloride along with 10⁻⁵ mols of a catalyst,tetraphenylphosphonium tetraphenyl borate (TPTB) added thereto. Next,methylene chloride was evaporated away, and a thin film having athickness of 0.01 cm was formed on the dish. Next, the thin-filmprepolymer was polymerized in melt in a reduced-pressure oven equippedwith a hot plate, at 270° C. and 0.5 Torr for 4 hours to obtain apolycarbonate. Its data are given in Table 1.

Comparative Example 1

The same process as in Example 1 was repeated. In this, however, theamount of DPC added to the reactor was 236 g (1.1 mols) and theprepolymer formed had a terminal hydroxyl fraction of 50%, and, in thesolid-phase polymerization step, 10⁻⁵ mols of tetraphenylphosphoniumtetraphenyl borate (TPTB) was used as the catalyst and thepolymerization time was 0.5 hours. The data of the polymer producedherein are given in Table 1.

Comparative Example 2

The same process as in Example 1 was repeated. In this, however, theamount of DPC added to the reactor was 236 g (1.1 mols) and theprepolymer formed had a terminal hydroxyl fraction of 61%. The data ofthe polymer produced herein are given in Table 1.

Comparative Example 3

The same process as in Example 1 was repeated. In this, however, nocatalyst was used in the solid-phase polymerization step, and thepolymerization time was 93 hours. The data of the polymer producedherein are given in Table 1.

Comparative Example 4

Not undergoing solid-phase polymerization, the monomers of Example 1were directly polymerized like in the process of prepolymer formation inExample 1. In this, however, tetramethylammonium hydroxide (0.5 mmols)and tetraphenylphosphonium tetraphenylborate (0.01 mmols) both servingas a catalyst were added to the reaction system, and the polymerizationtime under the vacuum degree of 0.5 Torr was 3 hours. The data of thepolymer produced herein are given in Table 1.

Example 4

228 g (1.0 mol) of bisphenol A (BPA), 1.23 g (0.004 mols) of 1,1,1-tris(4-hydroxyphenylethane) (THPE), 257 g (1.2 mols) of diphenyl carbonate(DPC) and 0.5 mmols of tetramethylammonium hydroxide (TMAH) were putinto a one liter nickel autoclave equipped with a stirrer, and purgedwith argon five times in all. Next, the mixture was heated at 190° C.and reacted for 30 minutes in the argon atmosphere. Next, this wasfurther heated gradually up to 235° C. and reacted for 60 minutes whilebeing degassed up to a vacuum degree of 60 Torr; then this was stillfurther heated gradually up to 270° C. and reacted for 120 minutes whilebeing degassed up to a vacuum degree of 10 Torr; and this was stillfurther reacted for 30 minutes while being degassed up to a vacuumdegree of 1 Torr and then for 30 minutes while being degassed up to avacuum degree of 0.5 Torr all at the same temperature of 270° C. Afterhaving been thus reacted, the system in the reactor was purged withargon to have an atmospheric pressure, and the prepolymer thus formedwas taken out and ground.

The viscosity-average molecular weight of the prepolymer was 10900, andthe terminal hydroxyl fraction thereof was 30%.

The prepolymer was dissolved in methylene chloride along with 0.0066 g(1×10⁻⁵ mols/BPA units) of cyclohexyltriphenylphosphonium tetraphenylborate (HPTB) serving as a solid-phase polymerization catalyst, to whichwas added n-heptane so as to deposit the prepolymer. After concentratedto be solid, this was dried in vacuum to obtain a powder of theprepolymer. 20 g of the powder was put into a SUS tube having a diameterof 58 mm and a length of 170 mm, into which was introduced nitrogen gasat a flow rate of 100 ml/min. In that condition, this was heated fromroom temperature up to 240° C., and polymerized in a solid phase for 4hours to obtain a polycarbonate. Its data are given in Table 2.

Example 5

The same process as in Example 4 was repeated, except that heptane gaswas introduced into the solid-phase polymerization system. The data ofthe polycarbonate thus produced herein are given in Table 1.

Comparative Example 5

Not undergoing solid-phase polymerization, the monomers of Example 4were directly polymerized like in the process of prepolymer formation inExample 4. In this, however, tetramethylammonium hydroxide (TMAH) (0.5mmols) and tetraphenylphosphonium tetraphenylborate (TPTB) (0.01 mmols)both serving as a catalyst were added to the reaction system, and thepolymerization time under the vacuum degree of 0.5 Torr was 3 hours. Thedata of the polymer produced herein are given in Table 1.

Example 6

228 g (1.0 mol) of bisphenol A (BPA), 10.6 g (0.05 mols) ofp-cumylphenol and 0.5 mmols of tetramethylammonium hydroxide (TMAH) wereput into a one liter nickel autoclave equipped with a stirrer, andpurged with argon five times in all. Next, the mixture was heated at190° C. and reacted for 30 minutes in the argon atmosphere. Next, thiswas further heated gradually up to 235° C. and reacted for 60 minuteswhile being degassed up to a vacuum degree of 60 Torr; then this wasstill further heated gradually up to 270° C. and reacted for 120 minuteswhile being degassed up to a vacuum degree of 10 Torr; and this wasstill further reacted for 30 minutes while being degassed up to a vacuumdegree of 1 Torr and then for 30 minutes while being degassed up to avacuum degree of 0.5 Torr all at the same temperature of 270° C. Afterhaving been thus reacted, the system in the reactor was purged withargon to have an atmospheric pressure, and the prepolymer thus formedwas taken out and ground.

The viscosity-average molecular weight of the prepolymer was8600, andtheterminal hydroxyl fraction thereof was 33%.

The prepolymer was dissolved in methylene chloride along with 0.0066 g(1×10⁻⁵ mols/BPA units) of cyclohexyltriphenylphosphonium tetraphenylborate (HPTB) serving as a solid-phase polymerization catalyst, to whichwas added n-heptane so as to deposit the prepolymer. After concentratedto be solid, this was dried in vacuum to obtain a powder of theprepolymer. 20 g of the powder was put into a SUS tube having a diameterof 58 mm and a length of 170 mm, into which was introduced nitrogen gasat a flow rate of 100 ml/min. In that condition, this was heated fromroom temperature up to 240° C., and polymerized in a solid phase for 4hours to obtain a polycarbonate. Its data are given in Table 3.

Example 7

The same process as in Example 6 was repeated, except that heptane gaswas introduced into the solid-phase polymerization system. The data ofthe polycarbonate thus produced herein are given in Table 3.

Example 8

The same process as in Example 6 was repeated, except thatp-tert-butylphenol but not p-cumylphenol was used. The data of thepolycarbonate thus produced herein are given in Table 3.

Example 9

The same process as in Example 6 was repeated, except thatp-tert-octylphenol but not p-cumylphenol was used. The data of thepolycarbonate thus produced herein are given in Table 3.

Comparative Example 6

Not undergoing solid-phase polymerization, the monomers of Example 6were directly polymerized like in the process of prepolymer formation inExample 6. In this, however, tetramethylammonium hydroxide (TMAH) (0.5mmols) and tetraphenylphosphonium tetraphenylborate (TPTB) (0.01 mmols)both serving as a catalyst were added to the reaction system, and thepolymerization time under the vacuum degree of 0.5 Torr was 3 hours. Thedata of the polymer produced herein are given in Table 3.

Example 10

228 g (1.0 mol) of bisphenol A (BPA), 246 g (1.15 mols) of diphenylcarbonate (DPC), 0.5 mmols of tetramethylammonium hydroxide (TMAH) and1×10⁻⁵ mols of tetraphenylphosphonium tetraphenyl borate (TPTB) were putinto a one liter nickel steel autoclave equipped with a stirrer, andpurged with argon five times in all. Next, the mixture was heated at190° C. and reacted for 30 minutes in the argon atmosphere. Next, thiswas further heated gradually up to 235° C. and reacted for 60 minuteswhile being degassed up to a vacuum degree of 60 Torr; then this wasstill further heated gradually up to 270° C. and reacted for 120 minuteswhile being degassed up to a vacuum degree of 10 Torr; and this wasstill further reacted for 30 minutes while being degassed up to a vacuumdegree of 1 Torr and then for 30 minutes while being degassed up to avacuum degree of 0.5 Torr all at the same temperature of 270° C. Afterhaving been thus reacted, the system in the reactor was purged withargon to have an atmospheric pressure, and the prepolymer thus formedwas taken out and ground.

The viscosity-average molecular weight of the prepolymer was 7200, andthe terminal hydroxyl fraction thereof was 30%.

8.04 g of the prepolymer was put on a SUS laboratory dish having adiameter of 32 cm, to which was added 10 ml of methylene chloride. Onthe dish, the prepolymer was dissolved in methylene chloride. Next,methylene chloride was evaporated away, and a thin film having athickness of 0.01 mm was formed on the dish. This was dried overnight at120° C. in vacuum. Next, the thin-film prepolymer was polymerized inmelt in a reduced-pressure oven equipped with a hot plate, at 270° C.and 0.5 Torr for 4 hours to obtain a polycarbonate. Its data are givenin Table 4.

Example 11

The same process as in Example 10 was repeated, except that the time forthin film melt polymerization of the prepolymer was 1 hour but not 4hours. The data of the polycarbonate produced herein are given in Table4.

Comparative Example 7

228 g (1.0 mol) of bisphenol A (BPA), 246 g (1.15 mols) of diphenylcarbonate (DPC), 0.5 mmols of tetramethylammonium hydroxide (TMAH) and1×10⁻⁵ mols of tetraphenylphosphonium tetraphenyl borate (TPTB) were putinto a one liter nickel steel autoclave equipped with a stirrer, andpurged with argon five times in all. Next, the mixture was heated at190° C. and reacted for 30 minutes in the argon atmosphere. Next, thiswas further heated gradually up to 235° C. and reacted for 60 minuteswhile being degassed up to a vacuum degree of 60 Torr; then this wasstill further heated gradually up to 270° C. and reacted for 120 minuteswhile being degassed up to a vacuum degree of 10 Torr; and this wasstill further reacted for 30 minutes while being degassed up to a vacuumdegree of 1 Torr and then for 3 hours while being degassed up to avacuum degree of 0.5 Torr all at the same temperature of 270° C. Afterhaving been thus reacted, the system in the reactor was purged withargon to have an atmospheric pressure, and the polycarbonate thus formedwas taken out. Its data are given in Table 4.

TABLE 1 Catalyst in Catalyst in Final Prepolymerization PolymerizationAmount Amount Viscosity- Terminal Acetone Cyclic Used Used averageHydroxyl Soluble Oligomer (mol/mol (mol/mol Molecular Fraction RemainingMonomers (ppm) Content Content Compound BPA) Compound BPA) Weight (Mv)(mol %) Phenol BPA DPC (wt. %) (wt. %) Example 1 TMAH 0.5 × 10⁻³ HPTB 1× 10⁻⁵ 19000 0.8 2 7 at most 1 1.0 0.11 Example 2 TMAH 0.5 × 10⁻³ HPTB 1× 10⁻⁵ 18500 8.6 10 30 30 2.0 0.13 Example 3 TMAH 0.5 × 10⁻³ TPTB 1 ×10⁻⁵ 21200 6.5 0 10 10 2.0 0.26 Comp. Ex. 1 TMAH 0.5 × 10⁻³ TPTB 1 ×10⁻⁵ 16500 50.0 110 130 110 — — Comp. Ex. 2 TMAH 0.5 × 10⁻³ HPTB 1 ×10⁻⁵ 26000 70.4 10 100 10 2.9 0.21 Comp. Ex. 3 TMAH 0.5 × 10⁻³ — — 1120025.3 10 100 at most 1 5.1 0.15 Comp. Ex. 4 TMAH 0.5 × 10⁻³ TPTB 1 × 10⁻⁵15900 20.0 at most 1 30 450 3.3 0.51 (Notes) TMAH: tetramethylammoniumhydroxide HPTB: cyclohexyltriphenylphosphonium tetraphenyl borate TPTB:tetraphenylphosphonium tetraphenyl borate BPA: bisphenol A DPC: diphenylcarbonate

TABLE 2 Catalyst in Catalyst in Final Prepolymerization PolymerizationAmount Amount Viscosity- Terminal Acetone Cyclic Used Used averageHydroxyl Soluble Oligomer (mol/mol (mol/mol Molecular Fraction RemainingMonomers (ppm) Content Content Compound BPA) Compound BPA) Weight (Mv)(mol %) Phenol BPA DPC (wt. %) (wt %) Example 4 TMAH 0.5 × 10⁻³ HPTB 1 ×10⁻⁵ 28800 8.0 10 10 10 1.2 0.12 Example 5 TMAH 0.5 × 10⁻³ HPTB 1 × 10⁻⁵29200 7.8 10 20 10 1.4 0.13 Comp. Ex. 5 TMAH 0.5 × 10⁻³ TPTB 1 × 10⁻⁵28200 15.1 20 30 230 3.2 0.45 (Notes) TMAH: tetramethylammoniumhydroxide HPTB: cyclohexyltriphenylphosphonium tetraphenyl borate TPTB:tetraphenylphosphonium tetraphenyl borate BPA: bisphenol A DPC: diphenylcarbonate

Viscosity- Acetone Cyclic Catalyst Used average Terminal FractionRemaining Soluble Oligomer Terminating Prepoly- Solid-phase Molecular(mol %) Monomers (ppm) Content Content Agent merization PolymerizationWeight (Mv) OH cumyl phenyl Phenol BPA DPC (wt. %) (wt. %) Example 6p-p-cumylphenol TMAH HPTB 26300 1.0 75.0 24.0 10 30 10 0.7 0.09 Example7 p-cumylphenol TMAH HPTB 25900 3.0 72.0 25.0 10 20 10 0.8 0.10 Example8 p-butylphenol TMAH HPTB 25500 2.0 71.0 27.0 10 20 20 1.0 0.11 Example9 p-octylphenol TMAH HPTB 32200 3.2 75.0 22.0 10 20 10 0.6 0.19 Comp.Ex. 6 p-cumylphenol TMAH TPTB 18000 20.0 54.0 26.0 10 30 240 3.2 0.46(Notes) TMAH: tetramethylammonium hydroxide HPTB:cyclohexyltriphenylphosphonium tetraphenyl borate TPTB:tetraphenylphosphonium tetraphenyl borate BPA: bisphenol A DPC: diphenylcarbonate

TABLE 4 Catalyst Catalyst in Final Prepolymerization PolymerizationAmount Amount Viscosity- Terminal Acetone Cyclic Used Used averageHydroxyl Soluble Oligomer (mol/mol (mol/mol Molecular Fraction RemainingMonomers (ppm) Content Content Compound BPA) Compound BPA) Weight (Mv)(mol %) Phenol BPA DPC (wt. %) (wt. %) Example 10 TMAH 0.5 × 10⁻³ — —21200 6.5  0 10 10 2.0 0.26 TPTB   1 × 10⁻⁵ Example 11 TMAH 0.5 × 10⁻³ —— 16500 13.4 10 10 10 2.5 0.28 TPTB   1 × 10⁻⁵ Comp. Ex. 7 TMAH 0.5 ×10⁻³ — — 15900 20.0 at most 1 30 450 3.3 0.51 TPTB   1 × 10⁻⁵ (Notes)TMAH: tetramethylammonium hydroxide HPTB: cyclohexyltriphenylphosphoniumtetraphenyl borate TPTB: tetraphenylphosphonium tetraphenyl borate BPA:bisphenol A DPC: diphenyl carbonate

INDUSTRIAL APPLICABILITY

According to the invention, provided are polycarbonates which contain areduced amount of impurities such as remaining monomers, oligomers andothers and which have improved physical properties including impactstrength, etc.

What is claimed is:
 1. A polycarbonate produced by preparing apolycarbonate prepolymer through prepolymerization followed bypolymerizing the prepolymer by solid-phase, swollen solid-phase or thinfilm melt-phase transesterification, of which a total of the dihydroxycompound content, dicarbonate content and monohydroxy compound contentis smaller than 100 ppm, and an acetone soluble content thereof is atmost 3.0% by weight when polymerization of the prepolymer is conductedby thin film melt-phase transesterification, or an acetone solublecontent thereof is at most 3.5% by weight when polymerization of theprepolymer is conducted by solid-phase or swollen solid-phasetransesterification.
 2. A polycarbonate produced by preparing apolycarbonate prepolymer through prepolymerization followed bypolymerizing the prepolymer through solid-phase, swollen solid-phase orthin film melt-phase transesterification, of which a dihydroxy compoundcontent is smaller than 100 ppm, and an acetone soluble content thereofis at most 3.0% by weight when polymerization of the prepolymer isconducted by thin film melt-phase transesterification, or an acetonesoluble content thereof is at most 3.5% by weight when polymerization ofthe prepolymer is conducted by solid-phase or swollen solid-phasetransesterification.
 3. A polycarbonate produced by transesterificationof a dihydroxy compound and a dicarbonate, of which an acetone solublecontent thereof is at most 2.0% by weight.
 4. A polycarbonate producedby preparing a polycarbonate prepolymer through prepolymerizationfollowed by polymerizing the prepolymer through solid-phase or swollensolid-phase transesterification, of which a terminal hydroxyl fractionis smaller than 2 mol %, and an acetone soluble content thereof is atmost 3.5% by weight.
 5. A polycarbonate produced by preparing apolycarbonate prepolymer through prepolymerization followed bypolymerizing the prepolymer through thin film melt-phasetransesterification, of which a terminal hydroxyl fraction is smallerthan 15 mol %, and an acetone soluble content thereof is at most 3.0% byweight.
 6. A polycarbonate produced by preparing a polycarbonateprepolymer through prepolymerization followed by polymerizing theprepolymer by solid-phase, swollen solid-phase or thin film melt-phasetransesterification, of which a cyclic oligomer content thereof is atmost 0.45% by weight, and an acetone soluble content thereof is at most3.0% by weight when polymerization of the prepolymer is conducted bythin film melt-phase transesterification, or an acetone soluble contentthereof is at most 3.5% by weight when polymerization of the prepolymeris conducted by solid-phase or swollen solid-phase transesterification.7. The polycarbonate of claim 1, wherein the polycarbonate prepolymer isprepared by thermal polymerization of (A) an aromatic dihydroxycompound, (B) a dicarbonate and (C) a monohydroxy compound.
 8. Thepolycarbonate of claim 2, wherein the polycarbonate prepolymer isprepared by thermal polymerization of (A) an aromatic dihydroxycompound, (B) a dicarbonate and (C) a monohydroxy compound.
 9. Thepolycarbonate of claim 6, wherein the polycarbonate prepolymer isprepared by thermal prepolymerization of (A) an aromatic dihydroxycompound, (B) a dicarbonate and (C) a monohydroxy compound.
 10. Apolycarbonate produced by preparing a polycarbonate prepolymer bythermal prepolymerization of (A) an aromatic dihydroxy compound, (B) adicarbonate and (C) a monohydroxy compound followed by polymerizing theprepolymer by solid-phase or swollen solid-phase transesterification, ofwhich a monohydroxy compound-based terminal fraction is at least 50 mol%, and an acetone soluble content thereof is at most 3.5% by weight. 11.A polycarbonate produced by preparing a polycarbonate prepolymer bythermal prepolymerization of (A) an aromatic dihydroxy compound, (B) adicarbonate and (C) a monohydroxy compound followed by polymerizing theprepolymer by solid-phase or swollen solid-phase transesterification, ofwhich a terminal hydroxy fraction is smaller than 15 mol %.
 12. Anoptical material, comprising the polycarbonate of claim
 1. 13. Anoptical material, comprising the polycarbonate of claim
 2. 14. Anoptical material, comprising the polycarbonate of claim
 3. 15. Anoptical material, comprising the polycarbonate of claim
 4. 16. Anoptical material, comprising the polycarbonate of claim
 5. 17. Anoptical material, comprising the polycarbonate of claim
 6. 18. Anoptical material, comprising the polycarbonate of claim
 7. 19. Anoptical material, comprising the polycarbonate of claim
 8. 20. Anoptical material, comprising the polycarbonate of claim
 9. 21. Thepolycarbonate of claim 1, wherein the polycarbonate prepolymer isprepared by thermal prepolymerization of (A) an aromatic dihydroxycompound, (B) a dicarbonate and (C) a poly-functional organic compoundhaving at least three functional groups.
 22. The polycarbonate of claim2, wherein the polycarbonate prepolymer is prepared by thermalprepolymerization of (A) an organic dihydroxy compound, (B) adicarbonate and (C) a poly-functional organic compound having at leastthree functional groups.
 23. The polycarbonate of claim 6, wherein thepolycarbonate prepolymer is prepared by thermal prepolymerization of (A)an aromatic dihydroxy compound, (B) a dicarbonate and (C) apoly-functional organic compound having at least three functionalgroups.
 24. A polycarbonate produced by preparing a polycarbonateprepolymer by thermal prepolymerization of (A) an aromatic dihydroxycompound, (B) a dicarbonate and (C) a poly-functional organic compoundhaving at least three functional groups, followed by polymerizing theprepolymer by solid-phase or swollen solid-phase transesterification, ofwhich a terminal hydroxyl fraction is smaller than 15 mol %, and anacetone soluble content thereof of at most 3.5% by weight.
 25. A blowmolding material, comprising the polycarbonate of claim
 21. 26. A blowmolding material, comprising the polycarbonate of claim 24.